1. Field of the Invention
The present invention relates to a method of executing a fuel injection control by detecting an acceleration state of an engine, and a fuel injection control apparatus, and more particularly, to a fuel injection control method and a fuel injection control apparatus which determines an acceleration state at a predetermined level or more for executing an accurate air-fuel ratio control so as to execute a fuel injection control.
2. Description of the Related Art
In recent years, a fuel supply system of an engine is generally provided with a fuel injection control apparatus and controlled in such a manner as to inject a fuel in correspondence to an air amount sucked into a combustion chamber on the basis of data detected by various monitors. However, in a transient state such as a rapid accelerating time or the like, it becomes frequently hard to keep an air-fuel ratio of an air-fuel mixture optimum due to a detection delay of a suction air amount and a time lag until a feed of the fuel injected into a suction pipe reaches a combustion chamber.
Accordingly, in order to make the fuel injection control apparatus detect the transient state mentioned above without delay so as to execute an increase of the injection fuel, there has been employed a method of determining this on the basis of a fluctuation of a throttle opening degree by using a throttle valve opening degree sensor. However, if the throttle opening degree sensor is provided in a fuel supply system, a manufacturing cost is largely increased, so that the structure tends to be disadvantageous in a view of a cost.
On the other hand, there is a method of determining the transient state of the engine on the basis of a fluctuation of a suction pipe pressure by arranging a pressure sensor in the suction air pipe. In this case, in order to do away with an influence of a pulsation within the suction air pipe, there has been executed a determination by integrating the suction air pipe pressure over one combustion cycle and comparing with an integrated value of the suction air pipe pressure in the preceding one combustion cycle.
Further, in Japanese Unexamined Patent Publication No. 2002-242749, there is proposed a method of determining a transient state of an engine by defining a plurality of angle positions about a rotating angle of a crank shaft of the engine as sampling positions of a suction air pipe pressure, storing each of the suction air pipe pressures sampled at each of the sampling positions, and comparing the suction air pipe pressure sampled at the same position as the position at one cycle before every samplings. Accordingly, the structure is not affected by the influence of the pulsation within the suction air pipe is prevented, and tends to immediately correspond to a generation of the transient state.
However, there is a case that the suction air pipe pressure is increased in spite that a compared difference of the suction air pipe pressure is small, for example, a case that a slow acceleration is executed or the like. Accordingly, in the determining method mentioned above, in the case that the rapid acceleration is executed in a condition that the suction air pipe pressure is increased, the pressure difference does not become large in spite that a practical suction air amount is increased, so that the accelerated state is not determined. Accordingly, there is a defect that an amount of the fuel is not increased and the air-fuel ratio becomes lean, so that a trouble such as a breathing or the like is generated.